Abstract: The putrescine and spermidine accumulate in higher plants in response to various stresses. The rise of putrescine (Put) is paralleled by an increase in the activity of arginine decarboxylase. The Put is as an organic cation, its accumulation is a response to acidification of the cytoplasm resulting from cation／anion imbalance in order to regulate cellular pH, perhaps, Put may have a key position in nitrogen metabolism which has not been fully realized yet.